Bolted duct joints

ABSTRACT

A first duct segment may include a first flange including a first planar mating face and a first recess. A second duct segment may include a second flange including a second planar mating face and a second recess. The first duct segment and the second duct segment may be installed in a gas turbine engine. A first E-seal may be inserted in the first recess, and a second E-seal may be inserted in the second recess. A gap may be measured between the first flange and the second flange. A flat shim may be selected based on the size of the gap. The flat shim may be inserted between the first flange and the second flange. A plurality of bolts may be inserted through the first flange, the flat shim, and the second flange to seal the first duct segment to the second-duct segment.

FIELD

The disclosure generally relates to gas turbine engines. Moreparticularly, the disclosure relates to bolted duct joints in a gasturbine engine.

BACKGROUND

Modern aircraft may utilize one or more gas turbine engines. Highpressure air from a compressor section of the engine may be directedthrough bleed ducts to various parts of the engine and the aircraft. Theducts may be subjected to high temperatures and pressures. The ducts mayexperience thermal growth, deflections during flight. Also, duringassembly it may be difficult to fit adjacent segments of a duct togetherdue to manufacturing and assembly tolerance stack-ups.

SUMMARY

A duct joint may comprise a first duct segment, a second duct segment, aflat shim, a first seal, and a second seal. The first duct segment mayinclude a first flange. The first flange may have a first recess. Thesecond duct segment may include a second flange. The second flange mayhave a second recess. The flat shim may be located between the firstflange and the second flange. The first seal may be located in the firstrecess. The second seal may be located in the second recess.

In various embodiments, the first seal may be in contact with a recessedface of the first flange and a first planar face of the flat shim. Thesecond seal may be in contact with a recessed face of the second flangeand a second planar face of the flat shim. The first seal and the secondseal may comprise E-seals. A thickness of the first flange maycorrespond to a gap between the first flange and the second flange. Thefirst duct segment and the second duct segment may be coupled to anengine case in a gas turbine engine. The flat shim may comprise anickel-chromium-based superalloy. A first mating surface of the firstflange may be in contact with a first planar surface of the flat shim,and a second mating surface of the second flange may be in contact witha second planar surface of the flat shim.

A bleed system for an aircraft may comprising a first duct segmentincluding a first flange, the first flange having a first recess, a flatshim configured to form a seal with the first flange, wherein the flatshim comprises a nickel-chromium-based superalloy, and a first E-seallocated in the first recess and between the first flange and the flatshim.

In various embodiments, the bleed system may further comprise a secondduct including a second flange. The second flange may have a secondrecess. A second E-seal may be located in the second recess. A matingsurface of the first flange may be in contact with a first planarsurface of the flat shim. The flat shim may be selected to have athickness corresponding to a size of a gap between the first flange andthe second flange. A bolt may be inserted through the first ductsegment, the flat shim, and the second duct segment. The first ductsegment may be coupled to an engine case in a gas turbine engine. Thefirst seal may be in contact with a recessed face of the first flangeand a first planar face of the flat shim.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

FIG. 1 illustrates a schematic cross-section view of a gas turbineengine in accordance with various embodiments;

FIG. 2 illustrates a perspective view of a duct joint in accordance withvarious embodiments;

FIG. 3 illustrates an exploded view of the duct joint of FIG. 2;

FIG. 4 illustrates a cross-section view of a portion of the duct jointof FIG. 2;

FIGS. 5A-5C illustrate exploded views of duct joints with flat shims ofdifferent thicknesses in accordance with various embodiments; and

FIG. 6 illustrates a process for coupling two duct segments together inaccordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of various embodiments herein makes referenceto the accompanying drawings, which show various embodiments by way ofillustration. While these various embodiments are described insufficient detail to enable those skilled in the art to practice theinventions, it should be understood that other embodiments may berealized and that logical, chemical and mechanical changes may be madewithout departing from the spirit and scope of the inventions. Thus, thedetailed description herein is presented for purposes of illustrationonly and not of limitation. For example, the steps recited in any of themethod or process descriptions may be executed in any order and are notnecessarily limited to the order presented. Furthermore, any referenceto singular includes plural embodiments, and any reference to more thanone component or step may include a singular embodiment or step. Also,any reference to attached, fixed, connected or the like may includepermanent, removable, temporary, partial, full and/or any other possibleattachment option. Additionally, any reference to without contact (orsimilar phrases) may also include reduced contact or minimal contact.

Systems and methods for connecting duct segments are disclosed. Adjacentduct segments may comprise bolted flanges. The flanges may comprise arecess. A seal may be inserted in the recess of each flange. A gapbetween the adjacent duct segments may be measured. A flat shim may beselected based on the size of the gap. The flat shim may be insertedbetween the adjacent duct segments to bridge the gap resulting from thestack-up of manufacturing and assembly tolerances.

Referring to FIG. 1, a gas turbine engine 100 (such as a turbofan gasturbine engine) is illustrated, according to various embodiments. Gasturbine engine 100 is disposed about axial centerline axis 120, whichmay also be referred to as axis of rotation 120. Gas turbine engine 100may comprise a fan 140, compressor sections 150 and 160, a combustionsection 180, and turbine sections 190, 191. Air compressed in thecompressor sections 150, 160 may be mixed with fuel and burned incombustion section 180 and expanded across turbine sections 190, 191.Additionally, bleed air may be removed from the compressor sections 150,160 through bleed ducts and used for various purposes such as anti-iceair for the engine inlet or wing leading edges, or to supply pressurizedenvironmental air to the aircraft cabin. Turbine sections 190, 191 mayinclude high pressure rotors 192 and low pressure rotors 194, whichrotate in response to the expansion. Turbine sections 190, 191 maycomprise alternating rows of rotary airfoils or blades 196 and staticairfoils or vanes 198. A plurality of bearings 115 may support spools inthe gas turbine engine 100. FIG. 1 provides a general understanding ofthe sections in a gas turbine engine, and is not intended to limit thedisclosure. The present disclosure may extend to all types of turbineengines, including turbofan gas turbine engines and turbojet engines,for all types of applications.

The forward-aft positions of gas turbine engine 100 lie along axis ofrotation 120. For example, fan 140 may be referred to as forward ofturbine section 190 and turbine section 190 may be referred to as aft offan 140. Typically, during operation of gas turbine engine 100, airflows from forward to aft, for example, from fan 140 to turbine section190. As air flows from fan 140 to the more aft components of gas turbineengine 100, axis of rotation 120 may also generally define the directionof the air stream flow.

Referring to FIG. 2, a duct joint 200 is illustrated according tovarious embodiments. A first duct segment 210 and a second duct segment250 may transmit hot, compressed bleed air from the compressor sectionof a gas turbine engine. The first duct segment 210 may comprise a firstpipe 220 and a first flange 230, and the second duct segment 250 maycomprise a second pipe 260 and a second flange 270. The first flange 230and the second flange 270 may be separated by a gap G.

Due to manufacturing and assembly or installation tolerances, when thefirst duct segment 210 and the second duct segment 250 are installed inthe engine, the gap G may be present between the first flange 230 andthe second flange 270. Forcing the first flange 230 and the secondflange 270 together to eliminate the gap G would create a preload on thefirst duct segment 210 and the second duct segment 250. The preload maylimit the amount of thermal growth and deflections that the ductsegments 210, 250 may withstand.

Inserting a flat shim 240 between the first flange 230 and the secondflange 270 may decrease the preload applied to the duct segments 210,250. The flat shim 240 is located in the gap G between the first flange230 and the second flange 270. The bleed air in the duct segments mayreach 1250° Fahrenheit (˜676° C.) or greater. The flat shim 240 maycomprise a material capable of withstanding high temperatures andpressures. The material may be a nickel-chromium-based superalloy, suchas INCONEL®. The flat shim 240 may have a thickness T. The thickness Tof the flat shim 240 may be selected to correspond to the size of thegap G at room temperature. Thus, after the duct segments 210, 250 havebeen installed, a thickness of a flat shim may be selected which maydecrease the preload on the duct segments.

A plurality of bolts 280 may be inserted through the first flange 230,the flat shim 240, and the second flange 270. The bolts 280 may betightened, and the first flange 230, the flat shim 240, the secondflange 270, and two seals (shown in FIGS. 3-5) may seal the ductsegments 210, 250.

Referring to FIG. 3, an exploded view of the duct joint 200 isillustrated according to various embodiments. The first flange 230 andthe second flange 270 may each comprise a planar mating surface 272 anda recess 274. The recess 274 may be defined by a recessed surface 276and an inner circumference 278. The duct joint 200 may comprise a firstseal 290 and a second seal 291. The second seal 291 may be locatedwithin the recess 274 in the second flange 270, and the first seal 290may be located within the recess in the first flange 230. In variousembodiments, the seals 290, 291 may comprise an E-seal, such as an AS1895 seal. E-seals may be annular and have a cross-section generally inthe shape of an “E.” The seals 290, 291 may comprise a high temperaturematerial, such as INCONEL® or an age hardening austenitic nickel-basedsuperalloy such as WASPALOY®. E-seals may have high flexibility andspring back characteristics, and thus may tolerate thermal growth andmay also be reusable. The flat shim 240 may comprise a planar face 242,244 on each side of the flat shim 240. The planar faces 242, 244 of theflat shim may contact the planar mating surfaces of 272 of the firstflange 230 and the second flange 270. The planar faces 242, 244 of theflat shim may also contact the seals 290, 291. The first flange 230 maycomprise first bolt holes 231, the flat shim 240 may comprise shim boltholes 241, and the second flange 270 may comprise second bolt holes 271.The plurality of bolts 280 may be inserted through the bolt holes 231,241, 271, and a plurality of nuts 282 may be used to tighten the bolts280.

Referring to FIG. 4, a section view of a bolt 280 in the duct joint 200is illustrated according to various embodiments. The first flange 230may comprise the planar mating surface 232, the recessed surface 236,and the inner circumference 238. The second flange 270 may comprise theplanar mating surface 272, the recessed surface 276, and the innercircumference 278. The flat shim 240 may be located between the firstflange 230 and the second flange 270. The first seal 290 may be locatedin the first recess 234 and may contact the recessed surface 236 of thefirst flange 230, the inner circumference 238 of the first flange 230,and the first planar face 242 of the flat shim. Similarly, the secondseal 291 may be located in the second recess 274 and may contact therecessed surface 276 of the second flange 270, the inner circumference278 of the second flange 270, and the second planar face 244 of the flatshim 240. The planar mating surface 232 of the first flange 230 maycontact the first planar face 242 of the flat shim 240, and the planarmating surface 272 of the second flange 270 may contact the secondplanar face 244 of the flat shim 240. The bolt 280 may be insertedthrough the first flange 230, the flat shim 240, and the second flange270, and the nut 282 may tighten the bolt 280. As the bolt 280 istightened, the first seal 290 may be partially compressed between thefirst flange 230 and the flat shim 240, and the second seal 291 may bepartially compressed between the second flange 270 and the flat shim240.

Referring to FIGS. 5A-5C, exploded views of the duct joint 200 withdifferent thickness shims are illustrated according to variousembodiments. After the first duct segment 210 and the second ductsegment 250 are installed, the gap between the first flange 230 and thesecond flange 270 may be measured. Depending on the size of the gap,different sized flat shims may be selected. For example, in FIG. 5A, thegap between the first flange 230 and the second flange 270 may be thegreatest of FIGS. 5A-5C, and the flat shim 240A having the largestthickness T1 may be selected and inserted between the first flange 230and the second flange 270. In FIG. 5B, the gap may be smaller than thatin FIG. 5A, and the elected flat shim 240B may have a medium thicknessT2. In FIG. 5C, the gap between the first flange 230 and the secondflange 270 may be the smallest of FIGS. 5A-5C, and the flat shim 240Chaving the smallest thickness T3 relative to T1 and T2 may be selected.

Prior to assembly of the duct joint 200, a variety of shims 240 may beprepared with varying thicknesses, the varying thicknesses addressingthe most likely range of needs for the thickness of shim 240, driven bythe varying gaps between duct flanges. Each of the shims 240 is simplein design, having two flat mating faces on each side, and do not requireany special geometry to create the seal with the ducts. The shims 240can be manufactured from sheet stock and cut to shape and drilled forthe bolt holes. Thus, it would not be overly expensive to prepare avariety of shim sizes and supply them in a kit to the installer of theduct system. Also, the flanges on the ducts and the seals do not need tochange with varying thicknesses of the shim 240. The shim 240 is theonly varying part in the combination of parts needed to permit a ductjoint with a varying gap between the ducts. As a further advantage, theseal design may perform reliably in the application with no impact insealing performance created by the varying thicknesses of the shim 240.

Referring to FIG. 6, a process 600 for coupling duct segments isillustrated according to various embodiments. A first duct segment maybe coupled to a first portion of an aircraft (step 610). The firstportion of the aircraft may be any portion of the aircraft, such as alow pressure compressor case, a high pressure compressor case, a wing, apylon, another duct segment, or any other suitable portion of theaircraft. A second duct segment may be coupled to a second portion ofthe aircraft (step 620). The second portion of the aircraft may be anyportion of the aircraft, such as a low pressure compressor case, a highpressure compressor case, a wing, a pylon, another duct segment, or anyother suitable portion of the aircraft. In various embodiments, thefirst duct segment or the second duct segment may be a portion of anengine case. A first seal may be inserted into a recess in the firstflange, and a second seal may be inserted into a recess in the secondflange (step 630).

A gap may be measured between a first flange of the first duct segmentand a second flange of the second duct segment (step 640). A flat shimmay be selected to be inserted into the gap (step 650). In variousembodiments, flat shims of various standard thicknesses may beavailable. A flat shim having a thickness closest to the size of the gapmay be selected. In various embodiments, the flat shim having thegreatest thickness which is less than the size of the gap may beselected. The flat shim may be inserted into the gap (step 660). One ormore bolts may be inserted through the first flange, the flat shim, andthe second flange (step 670). The bolts may be tightened, and the firstflange, the flat shim, and the second flange may form a duct joint whichseals the first duct segment to the second duct segment.

Although described primarily herein with reference to high temperatureapplications in aircraft, the systems and methods described herein maybe utilized to couple any ducting comprising bolted flanges.

In the detailed description herein, references to “one embodiment”, “anembodiment”, “various embodiments”, etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to affect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described. After reading the description, it will be apparentto one skilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent various functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the inventions. The scope of the inventions is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

I claim:
 1. A duct joint comprising: a first duct segment including afirst flange, the first flange having a first recess; a second ductsegment including a second flange, the second flange having a secondrecess; a flat shim located between the first flange and the secondflange; a first seal located in the first recess; and a second seallocated in the second recess.
 2. The duct joint of claim 1, wherein thefirst seal is in contact with a recessed face of the first flange and afirst planar face of the flat shim.
 3. The duct joint of claim 2,wherein the second seal is in contact with a recessed face of the secondflange and a second planar face of the flat shim.
 4. The duct joint ofclaim 1, wherein the first seal and the second seal comprise E-seals. 5.The duct joint of claim 1, wherein a thickness of the first flangecorresponds to a gap between the first flange and the second flange. 6.The duct joint of claim 1, wherein the first duct segment and the secondduct segment are coupled to an engine case in a gas turbine engine. 7.The duct joint of claim 1, wherein the flat shim comprises anickel-chromium-based superalloy.
 8. The duct joint of claim 1, whereina first mating surface of the first flange is in contact with a firstplanar surface of the flat shim, and wherein a second mating surface ofthe second flange is in contact with a second planar surface of the flatshim.
 9. A bleed system for an aircraft comprising: a first duct segmentincluding a first flange, the first flange having a first recess; a flatshim configured to form a seal with the first flange, wherein the flatshim comprises a nickel-chromium-based superalloy; and a first E-seallocated in the first recess and between the first flange and the flatshim.
 10. The bleed system of claim 9, further comprising: a second ductsegment including a second flange, the second flange having a secondrecess; and a second E-seal located in the second recess.
 11. The bleedsystem of claim 9, wherein a first mating surface of the first flange isin contact with a first planar surface of the flat shim.
 12. The bleedsystem of claim 10, wherein the flat shim is selected to have athickness corresponding to a size of a gap between the first flange andthe second flange.
 13. The bleed system of claim 10, further comprisinga bolt inserted through the first duct segment, the flat shim, and thesecond duct segment.
 14. The bleed system of claim 9, wherein the firstduct segment is coupled to an engine case in a gas turbine engine. 15.The bleed system of claim 9, wherein the first E-seal is in contact witha recessed face of the first flange and a first planar face of the flatshim.